Multiple star wavelength division multiplexing passive optical networks using a wavelength assignment method

Abstract

The present invention discloses a multiple star wavelength division multiplexing passive optical network system using a wavelength assignment method. In a multiple star wavelength division multiplexing passive optical network system using a wavelength assignment method according to the present invention, only one WDM-PON system can provide services for a plurality of subscribers who is distributed in a wide range of area through multiple starring, by setting one or more band for transmitting up-stream signals as an up-stream basic band and one or more band for transmitting down-stream signals as a down stream basic band, respectively, and by dividing each of the up-stream basic band and the down stream basic band into a plurality of wavelength sub-bands and assigning the divided sub-bands to different areas using a wavelength division multiplexer/de-multiplexer which splits a band into two or more sub-bands.

The invention claimed is: 
     
       1. A multiple star wavelength division multiplexing passive optical network system using a wavelength assignment method, the system comprising:
 an optical line termination (OLT) comprised of a first wavelength division multiplexer/de-multiplexer (WDM) and a plurality of first optical transceivers being connected to the first WDM; 
 a first remote node (RN) comprising a band splitting wavelength division multiplexer/de-multiplexer (BSWDM) being connected to the OLT by an optical fiber, wherein the BSWDM splits a wavelength band for certain down-stream signals into a plurality of first wavelength sub-bands and combines a plurality of second wavelength sub-bands, into which a wavelength band for certain up-stream signals is split, with the wavelength band for the certain up-stream signals; 
 a plurality of second RNs being connected to the first RN by a plurality of optical fibers, wherein each of the second RNs is comprised of a second WDM; and 
 a plurality of optical network terminations (ONTs) being connected to the plurality of the second RNs by a plurality of separate optical fibers, wherein each of the plurality of ONTs comprises a second optical transceiver, 
 wherein a guard band (λ gb ) positioned between an up-stream basic band being used for the wavelength band for the certain up-stream signals and a down-stream basic band being used for the wavelength band for the certain down-stream signals is given by a formula of λ gb =λ gi +m[λ gi +(n−1)×λ c ], 
 wherein n indicates a number of channels which exist within either the first wavelength sub-bands or the second wavelength sub-bands; 
 wherein λ gi  indicates a guard band positioned either between the first wavelength sub-bands split from the down-stream basic band or between the second wavelength sub-bands split from the up-stream basic band; 
 wherein λ c  indicates a wavelength interval between the channels; 
 wherein m is a natural number including number 0; 
 wherein the BSWDM at the first RN comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic, and each WDM at the second RNs comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic; 
 a free spectrum range (FSR) of the AWG at the second RNs is given by a formula of FSR=λ gi +(n−1)λ c  and is the same as a wavelength range of the wavelength sub-bands which are split by the BSWDM, and each of the plurality of AWGs at the second RNs have the same FSR characteristic as one another; 
 the second optical transceiver positioned at each ONT is the same type of an optical transceiver which splits only either the wavelength band for the certain up-stream signals or the wavelength band for the certain down-stream signals; and 
 the ONTs employ only a filter for splitting D-band in the wavelength band for the certain down-stream signals as the down-stream basic band and U-band in the wavelength band for the certain up-stream signals as the up-stream basic band, each of which is a basic band, independently of the split sub-bands. 
 
     
     
       2. The multiple star wavelength division multiplexing passive optical network system of  claim 1 , wherein a distributed-feedback laser diode (DFB LD) is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals. 
     
     
       3. The multiple star wavelength division multiplexing passive optical network system of  claim 1 , wherein a wavelength-locked Fabry-Perot laser diode (F-P LD) by an incoherent light source injected from outside is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals. 
     
     
       4. The multiple star wavelength division multiplexing passive optical network system of  claim 1 , wherein a spectrum-sliced light emission diode (LED) is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals. 
     
     
       5. The multiple star wavelength division multiplexing passive optical network system of  claim 1 , wherein a semiconductor optical amplifier into which an incoherent light source is injected from outside is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals. 
     
     
       6. The multiple star wavelength division multiplexing passive optical network system of  claim 1 , wherein one or more band different from the wavelength band for the certain up-stream signals and the wavelength band for the certain down-stream signals is used as either one or both of the wavelength band for the certain up-stream signals and the wavelength band for the certain down-stream signals. 
     
     
       7. The multiple star wavelength division multiplexing passive optical network system of  claim 1 , wherein one or more band different from the wavelength band for the certain up-stream signals and the wavelength band for the certain down-stream signals is used as a band for monitoring the multiple star wavelength division multiplexing passive optical network system. 
     
     
       8. A multiple star wavelength division multiplexing passive optical network system using a wavelength assignment method, the system comprising:
 an optical line termination (OLT) comprised of a first wavelength division multiplexer/de-multiplexer (WDM) and a plurality of first optical transceivers being connected to the first WDM; 
 a first remote node (RN) comprising a wavelength division multiplexer/de-multiplexer (WDM) being connected to the OLT by an optical fiber, wherein the WDM splits a wavelength band for certain down-stream signals into a plurality of wavelength sub-bands and combines a plurality of wavelength sub-bands, into which a wavelength band for certain up-stream signals is split, with the wavelength band for the certain up-stream signals; 
 a plurality of second RNs being connected to the first RN by a plurality of optical fibers, wherein each of the second RNs is comprised of a BSWDM; and 
 a plurality of optical network terminations (ONTs) being connected to the plurality of the second RNs by a plurality of separate optical fibers, wherein each of the plurality of ONTs comprises a second optical transceiver, 
 wherein a guard band (λ gb ) positioned between an up-stream basic band being used for the wavelength band for the certain up-stream signals and a down-stream basic band being used for the wavelength band for the certain down-stream signals is given by a formula of λ gb =λ gi +m[λ gi +(n−1)×λ c ], 
 wherein n indicates a number of channels which exist within either the first wavelength sub-bands or the second wavelength sub-bands; 
 wherein λ gi  indicates a guard band positioned either between the first wavelength sub-bands split from the down-stream basic band or between the second wavelength sub-bands split from the up-stream basic band; 
 wherein λ c  indicates a wavelength interval between the channels; and 
 wherein m is a natural number including number 0; 
 wherein the WDM at the first RN comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic, and each BDWDM at the second RNs comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic; 
 a free spectrum range (FSR) of the AWG at the second RNs is given by a formula of FSR=λ gi +(n−1)λ c  and is the same as a wavelength range of the wavelength sub-bands which are split by the BSWDM, wherein each of the plurality of AWGs at the second RNs have the same FSR characteristic as one another; 
 the second optical transceiver positioned at each ONT is the same type of an optical transceiver which splits only either the wavelength band for the certain up-stream signals or the wavelength band for the certain down-stream signals; and 
 the ONTs employ only a filter for splitting D-band in the wavelength band for the certain down-stream signals as the down-stream basic band and U-band in the wavelength band for the certain up-stream signals as the up-stream basic band, each of which is a basic band, independently of the split sub-bands.